There are two values of a for which the determinant, $Δ=\begin{vmatrix}1 & -2 & 5\\0 & a & -1\\0 & 4 & 2a\end{vmatrix}=86,$ then the sum of there values of a is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 0
$Δ=\begin{vmatrix}1 & -2 & 5\\0 & a & -1\\0 & 4 & 2a\end{vmatrix}=86⇒2a^2+4=86$
so $a^2=41$
$a=±\sqrt{41}$
$∑a_i=0$